During teleport event, gravity is disabled and WalkMethod
is stored in `teleport.navigation_mode` which is used later to reset
the status after execution. Calling teleport events consecutively
will change the initial WalkMethod value. So update it only on the
first call. Also remove `else condition` as it stops the previously running
teleport when the new teleport call fails to find a hit point.
Reviewed by: dfelinto, mano-wii
Differential Revision: https://developer.blender.org/D15574
ead3fc4a07